Biochemical and pharmacological profile of darexaban, an oral direct factor Xa inhibitor

Discovery and development of Factor Xa inhibitors (2015-2022)

As a pathological coagulation process, thrombus can lead to many serious diseases, including ischemic stroke, acute myocardial infarction (AMI), acute coronary syndrome (ACS), and deep venous thrombosis (DVT). And anticoagulant drugs are one of the most effective ways to prevent and treat these diseases. Although macromolecular anticoagulant drugs such as low molecular weight heparins (LMWHs) are widely used in the clinic, their characteristics of requiring injectable use hinder their further promotion in the clinic, and the disadvantages of oral anticoagulant drugs, such as warfarin and dabigatran etexilate, which can easily cause bleeding adverse effects, are also not addressed. Factor Xa (FXa) has gained attention because it lies at the intersection of the coagulation cascade pathways, whereas subsequently introduced Factor Xa inhibitors such as rivaroxaban and apixaban, among others, have gained market popularity because of their high potency for anticoagulation and high specificity for Factor Xa when administered orally. But some of the drawbacks that these Factor Xa inhibitors have simultaneously such as fewer indications and the lack of an effective reversal drug when bleeding occurs are urgently addressed. The development of new Factor Xa inhibitors therefore becomes one means of addressing these questions. This article summarizes the small molecule Factor Xainhibitors developed from 2015 to 2022, classifies them according to their scaffolds, focuses on the analysis of their structure-activity relationships, and provides a brief assessment of them.

Protective Effect of Rivaroxaban Against Amyloid Pathology and Neuroinflammation Through Inhibiting PAR-1 and PAR-2 in Alzheimer's Disease Mice

BACKGROUND

Recent studies have revealed that atrial fibrillation (AF) patients have a high risk of developing cognitive impairment, vascular dementia, and Alzheimer's disease (AD). Some reports suggest that the application of oral anticoagulant with an appropriate dose may have a preventive effect on AD. However, which oral anticoagulant drug is more appropriate for preventing AD and the underlying mechanism(s) is still unknown.

OBJECTIVE

The aim of the present study was to assess the treatment effect of rivaroxaban administration as well as investigate the roles of PAR-1 and PAR-2 in the AD + CAA mice model.

METHODS

In the present study, we compared a traditional oral anticoagulant, warfarin, and a direct oral anticoagulant (DOAC), rivaroxaban, via long-term administration to an AD with cerebral amyloid angiopathy (CAA) mice model.

RESULTS

Rivaroxaban treatment attenuated neuroinflammation, blood-brain barrier dysfunction, memory deficits, and amyloid-β deposition through PAR-1/PAR-2 inhibition in the AD + CAA mice model compared with warfarin and no-treatment groups.

CONCLUSION

The present study demonstrates that rivaroxaban can attenuate AD progress and can be a potential choice to prevent AD.

Factors Affecting the Formation and Treatment of Thrombosis by Natural and Synthetic Compounds

Venous thromboembolism (VTE) refers to deep vein thrombosis (DVT), whose consequence may be a pulmonary embolism (PE). Thrombosis is associated with significant morbidity and mortality and is the third most common cardiovascular disease after myocardial infarction and stroke. DVT is associated with the formation of a blood clot in a deep vein in the body. Thrombosis promotes slowed blood flow, hypoxia, cell activation, and the associated release of many active substances involved in blood clot formation. All thrombi which adhere to endothelium consist of fibrin, platelets, and trapped red and white blood cells. In this review, we summarise the impact of various factors affecting haemostatic disorders leading to blood clot formation. The paper discusses the causes of thrombosis, the mechanism of blood clot formation, and factors such as hypoxia, the involvement of endothelial cells (ECs), and the activation of platelets and neutrophils along with the effects of bacteria and reactive oxygen species (ROS). Mechanisms related to the action of anticoagulants affecting coagulation factors including antiplatelet drugs have also been discussed. However, many aspects related to the pathogenesis of thrombosis still need to be clarified. A review of the drugs used to treat and prevent thrombosis and natural anticoagulants that occur in the plant world and are traditionally used in Far Eastern medicine has also been carried out.

Surfing the Blood Coagulation Cascade: Insight into the Vital Factor Xa

Factor Xa (FXa) plays a key role in haemostasis, it is a central part of the blood coagulation cascade which catalyzes the production of thrombin and leads to clot formation and wound closure. Therefore, FXa is an attractive target for the development of new anticoagulant agents. In this review, we will first describe the molecular features of this fundamental protein in order to understand its mechanism of action, an essential background for the design of novel inhibitors by means of synthetic organic chemistry or using peptides obtained from recombinant methodologies. Then, we will review the current state of the synthesis of novel direct FXa inhibitors along with their mechanisms of action. Finally, approved reversal agents that aid in maintaining blood haemostasis by using these commercial drugs will also be discussed.

Effect of a new inhibitor of factor Xa zifaxaban, on thrombosis in the inferior vena cava in rabbits

In recent years, oral factor Xa inhibitors have become a research focus as anticoagulant drugs. Zifaxaban is the first oral FXa inhibitor to enter clinical trials in China. The aim of this study was to determine the inhibitory effect of zifaxaban on thrombosisthrough a model ofinferior vena cava (IVC) thrombosis in rabbits. IVC thrombosis model was established by electrical injury and stenosis, and zifaxaban was administered (p.o.) for 5 consecutive days, then coagulation indicators and bleeding were observed. The results showed that zifaxaban had obvious inhibitory effects on FXa, and had a significant inhibitory effect on IVC thrombosis induced by electrical damage and stenosis. The effect of zifaxaban was similar to that of rivaroxaban, but the bleeding side-effects of zifaxaban were less severe than those of rivaroxaban. Zifaxaban could prolong the prothrombin time and activated partial thromboplastin time of plasma similar to that of other oral FXa inhibitors. Zifaxaban had a significant inhibitory effect on FXa, but it had no obvious effect on other coagulation factors, major anticoagulant factors or fibrinolytic indices. Our results suggest that zifaxaban had specific inhibitory effects on FXa and inhibited IVC thrombosis in rabbits with its hemorrhagic effect was less than that of rivaroxaban. Zifaxaban is ecpected to be developed as a new drug for the prevention of deep venous thrombosis, providing more medication options for patients with such disease, more research is required to support it in the future.

Pre-clinical pharmacodynamic study of a novel oral factor Xa inhibitor zifaxaban

Zifaxaban is an orally active, direct Factor Xa (FXa) inhibitor that is in development for the prevention and treatment of arterial and venous thrombosis. This study was conducted to investigate the biochemical and pharmacological activity of zifaxaban. In vitro activity was evaluated by enzyme, platelet aggregation, and clotting assays. In vivo effects were examined in venous thrombosis, arteriovenous-shunt thrombosis, carotid thrombosis, and bleeding models in rats. Zifaxaban competitively inhibits human FXa (IC₅₀ = 11.1 nM) with > 10,000-fold greater selectivity than other serine proteases. It did not impair platelet aggregation induced by collagen, adenosine diphosphate (ADP) or arachidonic acid. It significantly prolonged clotting time, prothrombin time (PT), and activated partial thromboplastin time (APTT) in the plasma of humans, rabbits, and rats, with a relatively weak effect on thrombin time (TT). In venous thrombosis models in rats, zifaxaban strongly suppressed thrombus formation with ED₅₀ values of 3.09 mg/kg, and its best efficacy time occurred at 2 h after administration. In arteriovenous-shunt thrombosis and carotid thrombosis models in rats, it inhibited thrombus formation in a dose-dependent manner. And in the rat tail bleeding assay, it showed a trend of less bleeding than rivaroxaban at doses that achieved the same antithrombotic effect. In conclusion, zifaxaban is a selective and direct FXa inhibitor and a promising oral anticoagulant for the prophylaxis and treatment of thromboembolic diseases.

Plasma factor Xa inhibition can predict antithrombotic effects of oral direct factor Xa inhibitors in rabbit atherothrombosis models

We evaluated the relationship between antithrombotic effects and pharmacodynamic (PD) marker changes produced by the novel factor (F)Xa inhibitors darexaban (YM150) and rivaroxaban in a rabbit model of plaque disruption-induced arterial thrombosis. Animals were subjected to catheter-induced endothelial denudation via the femoral artery followed by a two-week high-cholesterol diet. Plaque disruption was induced by balloon angioplasty, and then stasis was achieved by ligation at the distal side of the injured segment. Darexaban and rivaroxaban were administered orally 1 hour (h) before and 9 h after plaque disruption, and their antithrombotic effects were evaluated 24 h after the initiation of ligation. Prothrombin time (PT), activated partial thromboplastin time (APTT), and plasma FXa activity were measured using blood samples collected before and 1 h after administration. Darexaban and rivaroxaban significantly reduced thrombus formation. The thrombus weight obtained in the 30 mg/kg darexaban group was comparable to that in the 1 mg/kg rivaroxaban group (2.17 ± 0.63 and 3.23 ± 1.64 mg, respectively, vs. 8.01 ± 1.08 mg in the control group). Plasma FXa activity correlated with the antithrombotic effects of darexaban and rivaroxaban, while PT only correlated with those of darexaban. Our findings suggest that the degree of plasma FXa inhibition may be useful for predicting antithrombotic effects of darexaban and rivaroxaban in arterial thrombosis. PT may also be useful in evaluating antithrombotic effects of darexaban in particular.

Darexaban (YM150) versus enoxaparin for the prevention of venous thromboembolism after total hip arthroplasty: a randomised phase IIb dose confirmation study (ONYX-3)

This double-blind, double-dummy, randomised, phase IIb study (NCT00902928) evaluated different dosing regimens of darexaban compared with enoxaparin (randomised 1:1:1:1:1 to 15 mg twice daily [bid], 30 mg once daily [qd], 30 mg bid or 60 mg qd or enoxaparin 40 mg qd) in patients undergoing elective total hip arthroplasty. Patients, investigators, pharmacists and sponsor were all blinded to treatment allocation. Darexaban administration started 6-10 hours (h) post-surgery. Enoxaparin 40 mg qd administration started 12 ± 2 h before surgery. Treatment continued for 35 days. Bilateral venography was performed on Day 10 ± 2. The primary efficacy outcome was total VTEs (composite of proximal/distal deep-vein thrombosis, pulmonary embolism) or death, at Day 12. Total VTE rates were similar across all groups. There was no apparent difference in efficacy between onceand twice-daily darexaban (odds ratio [OR] 1.00; 95% confidence interval [CI] 0.71–1.42; p=0.988), or total daily dose (30 mg/day vs 60 mg/day; OR 0.81; 95% CI 0.57–1.15; p=0.244). There was no significant difference in major and/or clinically relevant non-major bleeding between darexaban qd or bid, or between total daily doses of 30 mg or 60 mg, and also for any dosing regimen of darexaban vs enoxaparin. Darexaban was well tolerated, without signs of liver toxicity. In conclusion, darexaban, administered qd or bid, and at total daily doses of 30 mg or 60 mg, appears to be effective for VTE prevention and was well tolerated. Data suggest no significant differences between a once- or twice-daily dosing regimen.

Inhibitory effects of ASP6537, a selective cyclooxygenase-1 inhibitor, on thrombosis and neointima formation in rats

INTRODUCTION

Percutaneous coronary interventions (PCIs), such as balloon angioplasty and stent placement, are effective in the treatment of coronary artery disease. PCI has drawbacks, however, including acute thrombosis after the procedure and restenosis of the vascular lumen due to abnormal neointimal hyperplasia. ASP6537 is a selective COX-1 inhibitor that has been investigated as a possible candidate for clinical development as an antiplatelet agent. In the present study, we evaluated the in vivo antithrombotic effect of ASP6537 and its effect on neointima formation after balloon angioplasty.

MATERIAL AND METHODS

The antithrombotic effect of ASP6537 was examined using an arteriovenous shunt thrombosis model in rats while the effect of ASP6537 on neointima formation was evaluated in a rat carotid arterial balloon angioplasty model.

RESULTS

In the thrombosis study, ASP6537 dose-dependently decreased the protein content of the thrombus, while no prolongation of template bleeding time was observed. In the neointima study, ASP6537 reduced neointima formation.

CONCLUSIONS

ASP6537 may be a promising agent for the prevention of acute thrombosis and restenosis after PCI in place of aspirin.

An injectable in situ lipid phase transition system for sustained delivery of dabigatran etexilate with low burst release

The first report of dabigatran exilate sustained release injection that exhibited great potential in controlling initial burst release.

A Phase II, double-blind, randomized, parallel group, dose-finding study of the safety and tolerability of darexaban compared with warfarin in patients with non-valvular atrial fibrillation: the oral factor Xa inhibitor for prophylaxis of stroke in atrial fibrillation study 2 (OPAL-2)

BACKGROUND

Darexaban (YM150) is a novel oral anticoagulant that directly inhibits factor Xa.

OBJECTIVES

To investigate the optimal daily dose regimen of YM150 in subjects with non-valvular atrial fibrillation (NVAF).

METHODS

In this multicenter, double-blind, double-dummy, randomized, parallel-group, dose-confirmation study (NCT00938730), patients with NVAF were randomized to darexaban 15 mg bid, 30 mg qd, 30 mg bid, 60 mg qd, 60 mg bid or 120 mg qd, or warfarin qd. The primary endpoint was the incidence of adjudicated major and/or clinically relevant non-major bleeding events. Secondary endpoints included efficacy, pharmacodynamics, safety and tolerability.

RESULTS

A total of 1297 patients were randomized and finally included in the trial (median age, 66 [range 30-89] years; 68.8% male): 981 completed treatment for a median of 28 weeks (interquartile range, 24-36). At daily doses of 30-60 mg, darexaban bid resulted in fewer bleeding events than darexaban qd. For darexaban 120 mg, the bid regimen produced more bleeding events than the qd regimen. Although few efficacy endpoints occurred, these decreased with increasing daily darexaban dose. Darexaban decreased plasma D-dimer levels (index of thrombogenesis) after 4 weeks of treatment by 21.5-33.8% compared with baseline, which was comparable with warfarin at the higher darexaban doses. Darexaban was well tolerated with no liver toxicity.

CONCLUSIONS

In this Phase II study in patients with NVAF, a lower bleeding rate was observed in the 120 mg daily darexaban group compared with warfarin with a reduction in plasma D-dimer as marker for hemostasis. Further investigation of the optimal dose of darexaban for the prevention of stroke in patients with NVAF would need to be considered.

Latest developments in anticoagulant drug discovery

Thromboembolic diseases have increased in number over the past years. Oral anticoagulants impair the formation and progression of thrombotic processes and are therefore of great importance in the treatment of these diseases. Until recently, vitamin K antagonists were used to block the coagulation system. But these agents display a lot of interactions besides their narrow therapeutic range and have potential risk of hemorrhage complications. Therefore, other factors of the coagulation cascade are currently being explored as therapeutic targets for the development of novel anticoagulants. This review will provide an overview of new drugs promising more effectiveness in the treatment of arterial and venous embolism. Furthermore, pharmacodynamics and drug interactions regarding new anticoagulants will be reported.

Clinical Pharmacokinetics, Pharmacodynamics, Safety and Tolerability of Darexaban, an Oral Direct Factor Xa Inhibitor, in Healthy Elderly Japanese Subjects

The clinical pharmacokinetics, pharmacodynamics, safety and tolerability of darexaban after single and multiple once-daily doses of 60, 120, and 240 mg in healthy elderly Japanese subjects were assessed. Following oral administration, darexaban was rapidly and extensively metabolized to darexaban glucuronide, which is an active glucuronide metabolite. Plasma concentrations of darexaban glucuronide increased with dose, and Cmax and AUC increased dose-dependently after both single and repeated doses. Cumulative urinary excretion of darexaban glucuronide up to 24 hours after repeated doses ranged from 28.59% to 36.50%. PT-INR, aPTT, and FXa activity were prolonged or decreased dose-dependently after both single and repeated doses of darexaban. The time-profile of pharamcodynamic parameters closely followed the time-concentration profile of darexaban glucuronide. Five adverse events occurred in the present study (4: darexaban [16.7%]; 1: placebo [8.3%]), all of which were mild in severity and required no treatment.

Investigational anticoagulants for hematological conditions: a new generation of therapies

INTRODUCTION

The introduction of novel anticoagulants has had contrasting effects on the agents in the pipeline, fueling the development of some and sinking the others. The complexity of the coagulation cascade offers interesting inhibition choices that might become valid treatment options.

AREAS COVERED

This review will highlight some of the anticoagulants in the pipeline. Following the success of the direct thrombin and FXa inhibitors already in the market, new agents are being tested. These include AZD0837, betrixaban, letaxaban, darexaban, and LY517717. Targeting other components of the hemostatic pathway might lead to better safety profiles without influencing efficacy. Inhibitors to FVIIa-tissue factor (FVIIa/TF) complex, FIX, FXI, and FXII are being assessed. New inspiring inhibitors are antisense oligonucleotides (ASOs) and aptamers. These are highly specific agents with readily reversible effect and might be engineered to inhibit any coagulation factor. Currently tested ASOs and aptamers are inhibitors of FXI, FXII, thrombin, FIXa, and platelet GPIV.

EXPERT OPINION

Some of the agents in the pipeline offer valid treatment option for long-term therapy, overcoming some of the drawbacks of the novel anticoagulants. Research is being driven by an expanding market in the anticoagulation field that has been unexploited for a long time.

The pharmacokinetics of darexaban are not affected to a clinically relevant degree by rifampicin, a strong inducer of P-glycoprotein and CYP3A4

AIMS

We investigated the effects of rifampicin on the pharmacokinetics (PK) of the direct clotting factor Xa inhibitor darexaban (YM150) and its main active metabolite, darexaban glucuronide (YM-222714), which almost entirely determines the antithrombotic effect.

METHODS

In this open-label, single-sequence study, 26 healthy men received one dose of darexaban 60 mg on day 1 and oral rifampicin 600 mg once daily on days 4-14. On day 11, a second dose of darexaban 60 mg was given with rifampicin. Blood and urine were collected after study drug administration on days 1-14. The maximal plasma drug concentration (C(max)) and exposure [area under the plasma concentration-time curve from time zero to time of quantifiable measurable concentration; (AUC(last)) or AUC(last) extrapolated to infinity (AUC(∞))] were assessed by analysis of variance of PK. Limits for statistical significance of 90% confidence intervals for AUC and C(max) ratios were predefined as 80-125%.

RESULTS

Darexaban glucuronide plasma exposure was not affected by rifampicin; the geometric mean ratio (90% confidence interval) of AUC(last) with/without rifampicin was 1.08 (1.00, 1.16). The C(max) of darexaban glucuronide increased by 54% after rifampicin [ratio 1.54 (1.37, 1.73)]. The plasma concentrations of darexaban were very low (<1% of darexaban glucuronide concentrations) with and without rifampicin. Darexaban alone or in combination with rifampicin was generally safe and well tolerated.

CONCLUSIONS

Overall, rifampicin did not affect the PK profiles of darexaban glucuronide and darexaban to a clinically relevant degree, suggesting that the potential for drug-drug interactions between darexaban and CYP3A4 or P-glycoprotein-inducing agents is low.

Darexaban (YM150), an oral direct factor Xa inhibitor, has no effect on the pharmacokinetics of digoxin

To investigate the impact of the direct Factor Xa inhibitor darexaban administered in a modified-release formulation (darexaban-MR) on the pharmacokinetic (PK) profile of digoxin. In this Phase I, randomized, double-blind, two-period crossover study (8 days for each treatment, 10 days washout), 24 healthy subjects received darexaban-MR 120 mg once/day (qd) + digoxin 0.25 mg qd in one treatment period, and placebo + digoxin 0.25 mg qd in the other treatment period. Blood for PK assessment of digoxin and darexaban was obtained in serial profile on day 8, as well as pre-dose on day 6-7; urinary PK samples were obtained up to 24 h after the last dose on day 8. A lack of interaction was determined if 90 % confidence intervals (CIs) for the geometric mean ratios (GMR) of digoxin C max,ss and AUC0-24h,ss with and without darexaban-MR co-administration were within 0.80-1.25 limits. Pharmacodynamic activity was assessed by international normalized ratio and activated partial thromboplastin time. Twenty-three subjects completed the study. The GMR (90 % CI) for C max,ss and AUC0-24h,ss of digoxin plus darexaban versus digoxin plus placebo was 1.03 (90 % CI: 0.94-1.12) and 1.11 (90 % CI: 1.05-1.17), respectively. The 90 % CI for the GMRs fell within the limits of 0.80-1.25, indicating a lack of drug-drug interaction. Co-administration of digoxin with darexaban-MR was well tolerated, with no unexpected treatment-emergent adverse events or safety concerns. Co-administration of darexaban-MR did not impact the steady-state PK profile of digoxin.

Darexaban: anticoagulant effects in mice and human plasma in vitro, antithrombotic effects in thrombosis and bleeding models in mice and effects of anti-inhibitor coagulant complex and recombinant factor VIIa

Here, we investigated the anticoagulant effects of darexaban in mice and human plasma in vitro, effects of darexaban in thrombosis and bleeding models in mice, and reversal effects of anti-inhibitor coagulant complex (ACC) and recombinant factor VIIa (rFVIIa) on anticoagulant effects of darexaban. In mice, darexaban inhibited FXa activity in plasma with an ED50 value of 24.8 mg/kg. Both darexaban and warfarin prolonged prothrombin time (PT) at 3 mg/kg and 0.3 mg/kg/day, respectively. PT and activated partial thromboplastin time (aPTT) prolonged by darexaban were dose-dependently reversed by intravenously-administered rFVIIa, significantly so at 1 mg/kg. In a pulmonary thromboembolism (PE) mouse model, both darexaban and warfarin dose-dependently reduced the mortality rate, significantly so at 10 mg/kg and 3 mg/kg/day, respectively. In a FeCl3-induced venous thrombosis (VT) mouse model, darexaban (0.3-10 mg/kg) dose-dependently decreased the thrombus protein content, significantly so at doses of 3 mg/kg or higher. In a tail-transection mouse model, darexaban had no significant effect on the amount of blood loss at doses up to 10 mg/kg, while warfarin showed a dose-dependent increase in blood loss, significantly so from 1 mg/kg/day. Darexaban and its metabolite darexaban glucuronide significantly prolonged PT and aPTT in human plasma in vitro, and while rFVIIa concentration-dependently reversed the prolonged PT in this plasma, ACC dose-dependently reversed both PT and aPTT changes prolonged by darexaban. Taken together, these results suggest that darexaban has a potential to be an oral anticoagulant with a better safety profile than warfarin, and that rFVIIa and ACC may be useful as antidotes to darexaban in cases of overdose.

Antithrombotic effect of chikusetsusaponin IVa isolated from Ilex paraguariensis (Maté)

The triterpene chikusetsusaponin IVa was isolated from the fruit of Ilex paraguariensis. Using biochemical and pharmacological methods, we demonstrated that chikusetsusaponin IVa (1) prolongs the recalcification time, prothrombin time, activated partial thromboplastin time, and thrombin time of normal human plasma in a dose-dependent manner, (2) inhibits the amidolytic activity of thrombin and factor Xa upon synthetic substrates S2238 and S2222, (3) inhibits thrombin-induced fibrinogen clotting (50% inhibition concentration, 199.4 ± 9.1 μM), and (4) inhibits thrombin- and collagen-induced platelet aggregation. The results also indicate that chikusetsusaponin IVa preferentially inhibits thrombin in a competitive manner (K(i)=219.6 μM). Furthermore, when administered intravenously to rats, chikusetsusaponin IVa inhibited thrombus formation in a stasis model of venous thrombosis, although it did not induce a significant bleeding effect. Chikusetsusaponin IVa also prolonged the ex vivo activated partial thromboplastin time. Altogether, these data suggest that chikusetsusaponin IVa exerts antithrombotic effects, including minor hemorrhagic events. This appears to be important for the development of new therapeutic agents.